Spacecraft east-west radiator assembly

ABSTRACT

A heat transfer assembly for a spacecraft is disclosed. The assembly includes an equipment panel having an east end and a west end. East and west radiator panels are coupled to the east and west ends, respectively, of the equipment panel. The assembly also includes a plurality of flexible heat pipes each having a first rigid tube thermally coupled to the east radiator panel, a second rigid tube coupled to the equipment panel, a third rigid tube thermally coupled to the west radiator panel, a first flexible tube sealingly coupled between the first and second rigid tubes, and a second flexible tube sealingly coupled between the second and third rigid tubes. The equipment panel is configured to retain one or more equipment modules in thermal contact with the second rigid tube of at least one of the plurality of flexible heat pipes.

CROSS-REFERENCE TO RELATED APPLICATIONS

Not applicable.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not applicable.

BACKGROUND

1. Field

The present invention generally relates to heat-transfer systems and, inparticular, to a spacecraft radiator assembly with flexible heat pipes.

2. Description of the Related Art

Spacecraft in a geosynchronous earth orbit (GEO) typically operate suchthat one side continuously faces toward the ground as the satelliteorbits the Earth. Such a satellite will have a north-south axis that,while in orbit, is approximately parallel to the north-south rotationalaxis of the Earth and an east-west axis that is perpendicular to thenorth-south axis. As the satellite orbits the Earth, the east and westsides of the spacecraft will alternately face toward the Sun and, twelvehours later, face away from the Sun toward deep space.

As GEO spacecraft are frequently used for communication and observation,the designers must accommodate complex communications payloads withlarge number of components and high thermal dissipation requirements.For example, a direct-broadcast or broadband spot-beam communicationsspacecraft may require dissipation of 14 kW or more of heat from thepayload electronics. As is well known to those of skill in the art,“fixed” north and south radiator panels provide the most mass-efficientand cost-efficient heat rejection capability, and therefore their areais generally maximized within the constraints imposed by the launchvehicle fairing. However, it is often the case that additional heatrejection capability is required beyond what can be provided by suchnorth and south radiator panels.

One conventional approach to providing additional heat rejectioncapability is the addition of east and west radiator panels, as shown inthe exploded view in FIG. 1 of a conventional spacecraft. Because eastand west radiator panels receive direct sun exposure during each orbit,they are less effective than north and south radiator panels andtherefore operate at higher average temperatures for an equivalentthermal load. This generally limits the use of east and west radiatorpanels to equipment such as output multiplexers (OMUXs) that can operateat higher temperatures. In addition, east and west radiator panels tendto undergo large diurnal temperature fluctuations, as the individualpanels alternately face the Sun and deep space, and equipment that isthermally coupled to conventional east and west radiator panels mayrequire significant heater power to limit the temperature fluctuationsto an acceptable range.

Another drawback of conventional radiator panels is that, once theradiator panel is installed, it becomes difficult to access equipmentinside the spacecraft including the equipment that is mounted on theradiator panels themselves. This increases the cost and time requiredfor remove-and-replace operations that may be necessary duringintegration and test of a conventional spacecraft.

SUMMARY

The present invention generally relates to heat-transfer systems and, inparticular, to a spacecraft radiator assembly with flexible heat pipes.

It is desirable to provide an east-west heat transfer assembly (EWHTA)having east and west radiator panels that reduce the average temperatureas well as the temperature fluctuations seen with conventional panels.In addition, it is advantageous to provide the ability to mountequipment to be cooled by the east and west radiator panels in alocation that is separate from the panels themselves, taking advantageof what is generally wasted volume within the body of the spacecraft. Itis also beneficial to provide easier access to internal equipment duringspacecraft integration and test while maintaining all thermal systemconnections.

In certain aspects of the present disclosure, a heat transfer assemblyfor a spacecraft is disclosed. The assembly includes an equipment panelhaving an east end and a west end, an east radiator panel coupled to theeast end of the equipment panel, and a west radiator panel coupled tothe west end of the equipment panel. The assembly also includes aplurality of flexible heat pipes each having a first rigid tubethermally coupled to the east radiator panel, a second rigid tubecoupled to the equipment panel, a third rigid tube thermally coupled tothe west radiator panel, a first flexible tube sealingly coupled betweenthe first and second rigid tubes, and a second flexible tube sealinglycoupled between the second and third rigid tubes. The equipment panel isconfigured to retain one or more equipment modules in thermal contactwith the second rigid tube of at least one of the plurality of flexibleheat pipes.

In certain aspects of the present disclosure, a spacecraft is disclosedthat has a core structure, an east-west equipment panel having an eastend and a west end, an east radiator panel rotatably coupled to the eastend of the equipment panel, and a west radiator panel rotatably coupledto the west end of the equipment panel. The spacecraft also has aplurality of flexible heat pipes each comprising a first rigid tubethermally coupled to the east radiator panel, a second rigid tubecoupled to the equipment panel, a third rigid tube thermally coupled tothe west radiator panel, a first flexible tube sealingly coupled betweenthe first and second rigid tubes; and a second flexible tube sealinglycoupled between the second and third rigid tubes. The spacecraft alsohas one or more equipment modules thermally coupled to the second rigidtube of at least one of the plurality of flexible heat pipes.

In certain aspects of the present disclosure, a method of controllingthe temperature of an equipment module on a spacecraft is disclosed. Themethod includes the step of thermally coupling the equipment module to aflexible heat pipe that comprises a first rigid tube thermally coupledto an east radiator panel disposed on an external east surface of thespacecraft, a second rigid tube thermally coupled to a west radiatorpanel disposed on an external west surface of the spacecraft, and athird rigid tube coupled to the first and second rigid tubes by firstand second flexible tubes, respectively, wherein the equipment module isthermally coupled to the third rigid tube.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide furtherunderstanding and are incorporated in and constitute a part of thisspecification, illustrate disclosed embodiments and together with thedescription serve to explain the principles of the disclosedembodiments. In the drawings:

FIG. 1 is an exploded view of a spacecraft equipped with conventionaleast and west radiator panels.

FIG. 2 depicts an exemplary EWHTA according to certain aspects of thepresent disclosure.

FIG. 3 is a wire-frame view of another embodiment of an EWHTA accordingto certain aspects of the present disclosure.

FIG. 4 is a top view of an exemplary flexible heat pipe according tocertain aspects of the present disclosure.

FIG. 5 is a perspective view of an exemplary spacecraft with an EWHTAaccording to certain aspects of the present disclosure.

FIG. 6 is a cutaway top view of the spacecraft of FIG. 5 according tocertain aspects of the present disclosure.

FIG. 7 is an enlarged side view of a portion of equipment panel of theEWHTA of FIG. 5 according to certain aspects of the present disclosure.

DETAILED DESCRIPTION

The present invention generally relates to heat-transfer systems and, inparticular, to a spacecraft radiator assembly with flexible heat pipes.

The following description discloses embodiments of an east-westheat-transfer assembly that is particularly adapted for use on a GEOspacecraft. In certain embodiments, however, the same concepts andconstruction may be effectively used on other types of spacecraft aswell as other applications where radiator panels provide a source ofcooling.

The detailed description set forth below is intended as a description ofvarious configurations of the subject technology and is not intended torepresent the only configurations in which the subject technology may bepracticed. The appended drawings are incorporated herein and constitutea part of the detailed description. The detailed description includesspecific details for the purpose of providing a thorough understandingof the subject technology. However, it will be apparent to those skilledin the art that the subject technology may be practiced without thesespecific details. In some instances, well-known structures andcomponents are shown in block diagram form in order to avoid obscuringthe concepts of the subject technology. Like components are labeled withidentical element numbers for ease of understanding.

FIG. 1 is an exploded view of a spacecraft 10 equipped with conventionaleast and west radiator panels 30A and 30B. The “north”, “south,” “east,”and “west” directions are defined as indicated by the arrows. Thespacecraft 10 has a core structure 11 that, in this example, takes theform of a central cylinder 12 with a rectangular “Earth deck” 14attached to an end that continuously faces toward the ground and asecond deck 16 attached to the other end of the cylinder 12. A northradiator panel 22A is attached to a north equipment panel 20A and thento the north side of the core structure 11, and a south radiator panel22B is attached to a north equipment panel 20B and then to the southside of the core structure 11. Structural panels 18 are attached to theeast and west sides of the core structure 11 and fixed east and westradiator panels 30A, 30B are respectively attached to east and westequipment panels 32A, 32B and then attached, in this example, to thestructural panels 18. Communication reflectors 19A, 19B, and 19C aredeployably attached to the deck 16 such that each reflector establisheda line of communication toward the Earth. Other spacecraft componentsand subsystems, such as solar power arrays, have been omitted forclarity.

FIG. 2 depicts an exemplary EWHTA 100 according to certain aspects ofthe present disclosure. The “north”, “south,” “east,” and “west”directions are defined in FIG. 2 as indicated by the arrows to indicatethe operational orientation of the EWHTA 100 when installed in a GEOspacecraft (not shown in FIG. 2). The EWHTA 100 includes an equipmentpanel 115 and, in this example, two east radiator panels 130A, 130B thatmay also be referred to as the north-east radiator panel 130A andsouth-west radiator panel 130B. In certain embodiments, the north andsouth directions, i.e. a north-south axis, may be arbitrarily rotated ina plane that is perpendicular to an east-west axis without departingfrom the scope of this disclosure. The EWHTA 100 also includes two westradiator panels 120A, 120B. A plurality of flexible heat pipes 140 runfrom one of the east radiator panels 130A, 130B across the equipmentpanel 115 to one of the west radiator panels 120A, 120B. The routing ofthe flexible heat pipes 140 is discussed in greater detail with respectto FIG. 3. The construction of the flexible heat pipes 140 is discussedin greater detail with respect to FIG. 4. Also shown in FIG. 2 are twonorth-south panels 110A, 110B that, in certain embodiments, arethermally coupled to the equipment panel 115 such that heat absorbed bythe north-south panels 110A, 110B, for example from equipment modulesthermally coupled to the north-south panels 110A, 110B, may be conductedto the equipment panel 115 and then rejected to one of the east or westradiator panels.

FIG. 3 is a wire-frame view of another embodiment 101 of an EWHTAaccording to certain aspects of the present disclosure. In this view,the two east radiator panels 130A, 130B are shown only in outline so asto reveal the routing of the flexible heat pipes 140. The dashed-linebox labeled “3B” is shown in enlarged form in FIG. 6.

It can be seen that, in this embodiment, the flexible heat pipe 140Aruns from the north-west radiator panel 120A across the equipment panel115 and onto the north-east radiator panel 130A and the flexible heatpipe 140B runs from the south-west radiator panel 120B across theequipment panel 115 and onto the south-east radiator panel 130B. Incertain embodiments, the flexible heat pipe 140A may be coupled to thesouth-east radiator panel 130B in place of north-east radiator panel130A. In certain embodiments, the flexible heat pipe 140B may be coupledto the north-east radiator panel 130A in place of south-east radiatorpanel 130B. In certain embodiments, a plurality of flexible heat pipes140 run in parallel from one of the west radiator panels 120A, 120B toone of the east radiator panels 130A, 130B. The EWHTA 101 also includesformed heat pipes 150 mounted on the equipment panel 115. These formedheat pipes serve to couple the various flexible heat pipes 140 so as to,for example, minimize variations in temperature across the equipmentpanel 115. The configuration and function of these formed heat pipes 150are discussed in greater detail with respect to FIG. 6.

When a spacecraft that includes an EWHTA 101 or similar, the east andwest directions of the spacecraft will point at the Sun once per orbit.At one point in the orbit, the west radiator panels 120A, 120B aredirectly exposed to the Sun, which has an effective surface temperatureof approximately 5800 K (10,000° F.), and the east radiator panels 130A,130B will be partially exposed to deep space, which has an averagetemperature of approximately 3 K (−454° F.). The west radiator panels120A, 120B will absorb radiated energy from the Sun and theirtemperature will increase, while the east radiator panels 130A, 130Bwill reject heat to deep space and their temperature will decrease. Withreference to a conventional spacecraft 10 of FIG. 1, equipment moduleson the west equipment panel 32B that are thermally coupled to only thewest radiator panel 30B will be significantly heated by heat transferfrom the west radiator panel 30B as the temperature of the west radiatorpanel 30B exceeds the current temperature of those equipment modules.Equipment modules mounted on the east or west equipment panels 32A, 32Bmust therefore be able to survive high operational temperatures drivenby this absorption of heat from the Sun as there is not alternate sourceof cooling to offset the heating by the Sun. On the east side of theexample spacecraft 10, equipment modules on the east equipment panel32A, being thermally coupled to only the east radiator panel 30A will besignificantly cooled by heat transfer to the west radiator panel 30A asthe temperature of the east radiator panel 30A drops toward thetemperature of deep space. It is possible to minimize the reduction inthe operational temperature of the equipment on the equipment panel 30Awhile being cooled by deep space by attaching heaters (not shown in FIG.1 of 2) to either the equipment modules or the equipment panel 30A. Theuse of such heaters, however, places an additional load on the powersystem of the spacecraft 10. Even with the heaters, the temperaturerange between the minimum temperature seen by the equipment modules whentheir radiator panel is facing toward deep space and the maximumtemperature seen when their radiator panel is facing toward the Sun canbe quite large and affect, for example, the reliability and performanceof the equipment module.

In contrast, a spacecraft with an EWHTA 100 will expose equipmentmodules coupled to east and west radiators 120A, 120B, 130A, 130B to asmaller temperature range, compared to equipment modules coupled toconventional east and west radiators 30A, 30B on the spacecraft 10. Inthe example where the west side of the spacecraft is facing toward theSun, the west radiator panels 120A, 120B heat up due to absorption ofheat from the Sun. This absorbed heat, however, is transferred all theway to the east radiation panels 130A, 130B by the flexible heat pipes140. This direct transfer of heat from the heated west radiator panels120A, 120B to the cooled east radiation panels 130A, 130B reduces themaximum temperature seen by the west radiator panels 120A, 120B andsimultaneously increases the minimum temperature seen by the eastradiation panels 130A, 130B while in this orientation to the Sun. Theequipment modules that are thermally coupled to the equipment panel 115will, therefore, see a smaller range of temperatures as the position ofthe Sun, relative to the spacecraft, moves between the west side and theeast side. In addition, the use of heaters to maintain the temperatureof the equipment modules above a minimum operational temperature will bereduced, if not eliminated, as the transferred heat from the hotradiation panels, in this example west radiator panels 120A, 120B, tothe cold radiation panels, in this example west radiator panels 130A,130B, will increase the minimum temperature seen by the radiation panelsand, therefore, the minimum temperature seen by the equipment moduleseven in the absence of heaters.

A series of thermal simulations were performed for equipment modulesmounted on a conventional east radiator panel 30A, such as shown in FIG.1 and the same equipment modules mounted on an EWHTA 100. Thesimulations determined the maximum and minimum temperatures seen by theequipment modules and the amount of additional heater power required tolimit the temperature swing of the equipment modules to less than 30° C.(86° F.). Simulations were run for the following cases:

conditions of simulation acronym vernal equinox, end-of-life performanceVEEOL summer solstice, beginning-of-life performance SSBOL autumnalequinox, beginning-of-life performance AEBOL winter solstice,beginning-of-life performance WSBOL

Table 1 lists the predicted minimum and maximum temperatures and theheater power required to maintain the temperature of the equipmentmodules within the allowable temperature swing. Predicted values thatexceed the limits are shown in boldface. In will be apparent that theconventional system allows the maximum temperature of the equipmentmodules to exceed the maximum limit while still requiring significantheater power during the portion of the orbit while the associatedradiator panel 30A, 30B is facing deep space. In contrast, the system ofthe present disclosure requires only a relatively small amount of heaterpower and only during the vernal equinox conditions.

TABLE 1 Temperature performance of east-west radiator systems MaxDiurnal Max Heater Min Max allowable temp allowable power Analysis temptemp temp swing swing required Configuration case (deg C.) (deg C.) (degC.) (deg C.) (deg C.) (W) System VEEOL 52 83 90 32 30 12 W according toSSBOL 44 59 90 16 30 None the present AEBOL 38 62 90 25 30 Nonedisclosure WSBOL 57 81 90 25 30 None Conventional VEEOL 47 107 90 62 30195 W  design SSBOL 34 74 90 41 30 66 W AEBOL 33 76 90 43 30 65 W WSBOL46 105 90 59 30 178 W 

FIG. 4 is a top view of an exemplary flexible heat pipe 140 according tocertain aspects of the present disclosure. The flexible heat pipe 140comprises a first rigid tube 141A, a second rigid tube 141C, a thirdrigid tube 141E, a first flexible tube 141B sealingly coupled betweenthe first and second rigid tubes 141A, 141C, and a second flexible tube141D sealingly coupled between the second and third rigid tubes 141C,141E. The first and third rigid tubes 141A, 141E are each closed at anoutboard end. The assembly of tubes 141A-141E form a sealed interiorvolume (not visible in FIG. 4) that contains a heat transfer fluid. Incertain embodiments, the flexible heat pipe contains a wick (not visiblein FIG. 4) that creates a gas-phase passage and a liquid-phase passagewithin the interior volume that facilitates the transfer of theliquid-phase heat transfer fluid from the colder portion(s) of theflexible heat pipe 140 to the hotter portion(s) of the flexible heatpipe 140. In certain embodiments, the first and second flexible tubes141B, 141D are configured such that the adjacent rigid portions 141A and141C and 141E can be rotated with respect to each other over a range ofangles without disconnection of the various elements of the flexibleheat pipe 140. In certain embodiments, the rigid tube 141A can be movedover a range of angles with respect to rigid tube 141C. In certainembodiments, rigid tube 141A can be oriented at any angle between 0°,i.e. extending straight out from, and 90° with respect to rigid tube141C. In certain embodiments, the rigid tube 141A can be moved over arange of −90° to +90° with respect to rigid tube 141C.

FIG. 5 is a perspective view of an exemplary spacecraft 200 with a EWHTA100 according to certain aspects of the present disclosure. The eastradiator panels 130A, 130B have been removed to expose the innerelements of the spacecraft 200. It will be apparent that the centralcylinder 220 has been vertically split, compared to the central cylinder12 of FIG. 1, by the introduction of the equipment panel 115 thatextends from the Earth deck 14 downward through the split mid-deck 210.

FIG. 6 is a cutaway top view of the spacecraft 200 of FIG. 5 accordingto certain aspects of the present disclosure. The view is taken justbelow the Earth deck 14 and faces downward, with certain elementsremoved for clarity. The middeck 210 is visible in the middle, with thenorth and south equipment panels 20A, 20B and north and south radiatorpanels 22A, 22B positioned at the top and bottom, in the orientation ofthis view. Various pieces of equipment 60 are mounted to the north andsouth equipment panels 20A, 20B.

An EWHTA 100 is visible in the middle of the spacecraft 200, with theequipment panel 115 passing left-to-right in this view across the middleof the middeck 210. The north-west radiator panel 120B is shown in an“open” position, with the closed position 122 shown in dashed line. Aflexible heat pipe 141 is shown with the rigid tube 141A embedded withinthe open radiator panel 122, and with the closed position 143 of thesame rigid tube 141A shown in dashed line. Representative equipmentmodules 50A and 50B are shown mounted to the equipment panel 115 andthermally coupled to the rigid tube 141C of the flexible heat pipe 100,which is shown as embedded within the panel 115. Embedding the rigidpipe 141C within the equipment panel 115 may provide greater flexibilityin positioning equipment on the panel, as well as the potential to mountequipment to both sides of the equipment panel 115 with equal thermalperformance. In certain embodiments, the rigid portions of heat pipe 141may be mounted to an inner or outer surface of one or more of theradiators 120B, 130B or to one of the surfaces of the equipment panel115. Mounting the heat pipe on the surface may provide a benefit inmanufacture or assembly of the radiators 120,b, 130B or equipment panel115. As an example, the rigid tube 141E is shown as mounted on the innersurface of radiator 130B, for example by bolting and thermally bondingwith brackets (not shown in FIG. 6). Other means of thermally couplingthe various portions of heat pipe 141 to the respective radiators andpanels will be apparent to those of skill in the art. The mounting ofequipment modules 50A and 50B is discussed in greater detail withrespect to FIG. 7. It will be apparent how the flexible tube 141B,positioned proximate to the hinge of the radiator panel 122, enables theradiator panel 122 to be opened without requiring prior removal ofequipment or the flexible heat pipe 141, thus simplifying the process ofgaining access to the equipment within the spacecraft 200.

FIG. 7 is an enlarged side view of a portion of equipment panel 115 ofthe EWHTA 100 of FIG. 5 according to certain aspects of the presentdisclosure. The rigid tubes 141C are shown for multiple flexible heatpipes 141, wherein the nomenclature of “141C-x” indicates individualflexible heat pipes 141. The arrows at the left and right section-linesindicate which radiator panel each line is connected to. For example,the first flexible heat pipe 141, identified as “141C-1” is thermallycoupled to north-west radiator panel 120A on the left and to north-eastradiator panel 130A on the right. The flexible heat pipes 141 arearranged in pairs, for example flexible heat pipes 141C-1 and 141C-2,which are respectively coupled to the northern and southern of the eastand west radiator panels.

The dashed-line boxes 50A and 50B indicate where the representativeelectronics modules 50A and 50B shown in FIG. 5 are mounted. Electronicsmodule 50A is mounted over, and thermally coupled to, the flexible heatpipes 141C-1, 141C-2, 141C-3, and 141C-4. If the equipment module 50A isconsidered to be at a uniform temperature across its base, then theequipment module 50A will transfer heat to each of the four flexibleheat pipes 141C-1, 141C-2, 141C-3, and 141C-4. This provides redundancyin the event that performance of one of the flexible heat pipes 141 isdegraded, for example by loss of the heat transfer fluid in thatflexible heat pipe 141. Equipment module 50B is coupled to only twoflexible heat pipes 141C-1 and 141C-2. In certain embodiments, theequipment modules 50A and 50B are attached to the support structure ofequipment panel 115 and simply held in thermal contact with the rigidtubes 141C of the various flexible heat pipes. In certain embodiments,the equipment modules 50A and 50B may be attached directly to the rigidtubes 141C of one or more of the flexible heat pipes 141. In certainembodiments, additional thermal coupling elements, for example shapedcopper straps or thermal grease, may be provided to improve the thermalcoupling of the equipment modules 50A, 50B to the respective rigid tubes141C.

In certain embodiments, formed heat pipes 150 thermally couple one ofeach pair of flexible heat pipes 141 to one of the adjacent pairs. Inthis embodiment, a first portion of a formed heat pipe 150-2 isthermally coupled to the flexible heat pipe 141C-2 of one pair and asecond portion of the formed heat pipe 150-2 is coupled to flexible heatpipe 141C-3 of an adjacent pair, with a short vertical portion joiningthe first and second portions. This provides additional redundancyacross the plurality of flexible heat pipes 141, in the event that oneof the flexible heat pipes 141 fails, and also serves to distribute heatacross the EWHTA 100 more evenly. For example, if the equipment module50B was dissipating a large amount of heat, the flexible heat pipes141C-1 and 141C-2 would be running hotter than the adjacent heat pipes141C-3 and 141C-4. The formed heat pipe 150-2 will transfer some of theheat from flexible heat pipe 141C-2 to flexible heat pipe 141C-3,thereby assisting is transferring this heat to the radiator panels 120A,120B, 130A, 130B.

The disclosed examples of an east-west heat transfer assembly illustrateexemplary configurations wherein heat from spacecraft equipment modulesis rejected through east-facing and west-facing radiator panels withoutsubjecting the equipment modules to the temperature extremes or largetemperature swings seen with conventional designs. With one of the eastand west radiator panels always facing toward deep space, the heatreceived by the Sun-facing radiator panel is transferred to the otherradiator panel and rejected to deep space rather than being transferredinto the equipment modules. This provides the additional benefit ofreducing or eliminating the need for heater power to maintain theequipment modules within a certain temperature range. While thedisclosed configurations include pairs of radiator panels on each of theeast and west sides of the spacecraft, it will be apparent to those ofskill in the art that the number, size, and location of the radiatorpanels can be varied without departing from the scope of thisdisclosure. In addition, the same principles and designs can be appliedto the north-facing and south-facing radiator panels of a GEO spacecraftor to a non-orbiting spacecraft to provide easy access to the interiorof the spacecraft without prior removal or disassembly of the thermalcontrol system.

This application includes description that is provided to enable aperson of ordinary skill in the art to practice the various aspectsdescribed herein. While the foregoing has described what are consideredto be the best mode and/or other examples, it is understood that variousmodifications to these aspects will be readily apparent to those skilledin the art, and the generic principles defined herein may be applied toother aspects. It is understood that the specific order or hierarchy ofsteps or blocks in the processes disclosed is an illustration ofexemplary approaches. Based upon design preferences, it is understoodthat the specific order or hierarchy of steps or blocks in the processesmay be rearranged. The accompanying method claims present elements ofthe various steps in a sample order, and are not meant to be limited tothe specific order or hierarchy presented. Thus, the claims are notintended to be limited to the aspects shown herein, but are to beaccorded the full scope consistent with the language claims.

Headings and subheadings, if any, are used for convenience only and donot limit the invention.

Reference to an element in the singular is not intended to mean “one andonly one” unless specifically so stated, but rather “one or more.” Useof the articles “a” and “an” is to be interpreted as equivalent to thephrase “at least one.” Unless specifically stated otherwise, the terms“a set” and “some” refer to one or more.

Terms such as “top,” “bottom,” “upper,” “lower,” “left,” “right,”“front,” “rear” and the like as used in this disclosure should beunderstood as referring to an arbitrary frame of reference, rather thanto the ordinary gravitational frame of reference. Thus, a top surface, abottom surface, a front surface, and a rear surface may extend upwardly,downwardly, diagonally, or horizontally in a gravitational frame ofreference.

Although the relationships among various components are described hereinand/or are illustrated as being orthogonal or perpendicular, thosecomponents can be arranged in other configurations in some embodiments.For example, the angles formed between the referenced components can begreater or less than 90 degrees in some embodiments.

Although various components are illustrated as being flat and/orstraight, those components can have other configurations, such as curvedor tapered for example, in some embodiments.

Pronouns in the masculine (e.g., his) include the feminine and neutergender (e.g., her and its) and vice versa. All structural and functionalequivalents to the elements of the various aspects described throughoutthis disclosure that are known or later come to be known to those ofordinary skill in the art are expressly incorporated herein by referenceand are intended to be encompassed by the claims. Moreover, nothingdisclosed herein is intended to be dedicated to the public regardless ofwhether such disclosure is explicitly recited in the claims. No claimelement is to be construed under the provisions of 35 U.S.C. §112, sixthparagraph, unless the element is expressly recited using the phrase“means for” or, in the case of a method claim, the element is recitedusing the phrase “operation for.”

A phrase such as an “aspect” does not imply that such aspect isessential to the subject technology or that such aspect applies to allconfigurations of the subject technology. A disclosure relating to anaspect may apply to all configurations, or one or more configurations. Aphrase such as an aspect may refer to one or more aspects and viceversa. A phrase such as an “embodiment” does not imply that suchembodiment is essential to the subject technology or that suchembodiment applies to all configurations of the subject technology. Adisclosure relating to an embodiment may apply to all embodiments, orone or more embodiments. A phrase such as an embodiment may refer to oneor more embodiments and vice versa.

The word “exemplary” is used herein to mean “serving as an example orillustration.” Any aspect or design described herein as “exemplary” isnot necessarily to be construed as preferred or advantageous over otheraspects or designs.

All structural and functional equivalents to the elements of the variousaspects described throughout this disclosure that are known or latercome to be known to those of ordinary skill in the art are expresslyincorporated herein by reference and are intended to be encompassed bythe claims. Moreover, nothing disclosed herein is intended to bededicated to the public regardless of whether such disclosure isexplicitly recited in the claims. No claim element is to be construedunder the provisions of 35 U.S.C. §112, sixth paragraph, unless theelement is expressly recited using the phrase “means for” or, in thecase of a method claim, the element is recited using the phrase “stepfor.” Furthermore, to the extent that the term “include,” “have,” or thelike is used in the description or the claims, such term is intended tobe inclusive in a manner similar to the term “comprise” as “comprise” isinterpreted when employed as a transitional word in a claim.

Although embodiments of the present disclosure have been described andillustrated in detail, it is to be clearly understood that the same isby way of illustration and example only and is not to be taken by way oflimitation, the scope of the present invention being limited only by theterms of the appended claims.

What is claimed is:
 1. A heat transfer assembly for a spacecraft,comprising: an equipment panel having an east end and a west end; aneast radiator panel coupled to the east end of the equipment panel; awest radiator panel coupled to the west end of the equipment panel; anda plurality of flexible heat pipes each comprising a first rigid tubethermally coupled to the east radiator panel, a second rigid tubecoupled to the equipment panel, a third rigid tube thermally coupled tothe west radiator panel, a first flexible tube sealingly coupled betweenthe first and second rigid tubes, and a second flexible tube sealinglycoupled between the second and third rigid tubes, wherein the equipmentpanel is configured to retain one or more equipment modules in thermalcontact with the second rigid tube of at least one of the plurality offlexible heat pipes.
 2. The heat transfer assembly of claim 1, wherein:each of the plurality of flexible heat pipes comprises: a sealed firstinternal volume formed by the respective first, second, and third rigidtubes and the first and second flexible tubes; and a first heat transferfluid disposed within the first internal volume; and the first and thirdrigid tubes of each of the plurality of flexible heat pipes are eachcapable of condensing the first heat transfer fluid from a vapor to aliquid by rejecting heat to the respective east and west radiatorpanels.
 3. The heat transfer assembly of claim 2, wherein the secondrigid tube of each of the plurality of flexible heat pipes is capable ofevaporating the first heat transfer fluid from a liquid to a vapor byaccepting heat from one or more equipment modules thermally coupled tothe second rigid tube.
 4. The heat transfer assembly of claim 2, whereinthe first and third rigid tubes of each of the plurality of flexibleheat pipes are each capable of evaporating the first heat transfer fluidfrom a liquid to a vapor by accepting heat from the respective east andwest radiator panels.
 5. The heat transfer assembly of claim 1, furthercomprising a plurality of formed heat pipes each comprising a firstportion thermally coupled to the second rigid tube of a first flexibleheat pipe, a second portion thermally coupled to the second rigid tubeof a second flexible heat pipe and a third portion sealingly coupledbetween the first and second portions.
 6. The heat transfer assembly ofclaim 5, wherein each of the plurality of formed heat pipes is capableof transferring heat from the hotter of the first and second flexibleheat pipes to the colder of the first and second flexible heat pipes. 7.The heat transfer assembly of claim 5, wherein: each of the plurality offormed heat pipes further comprises a sealed second interior volumeformed by the first, second, and third portions of the respective formedheat pipe and a second heat transfer fluid disposed within the secondinternal volume; each of the first and second portions is capable ofevaporating the heat transfer fluid from a liquid to a vapor byaccepting heat from the respective flexible heat pipe when therespective flexible heat pipe is the hotter of the first and secondflexible heat pipes; and each of the first and second portions iscapable of condensing the heat transfer fluid from a vapor to a liquidby rejecting heat to the respective flexible heat pipe when therespective flexible heat pipe is the colder of the first and secondflexible heat pipes.
 8. The heat transfer assembly of claim 1, whereinat least one of the east and west radiator panels is hingedly coupled tothe equipment panel such that the at least one of the east and westradiator panels can be rotated with respect to the equipment panel. 9.The heat transfer assembly of claim 1, wherein the east and westradiator panels are rotatably coupled to the respective east and westends of the equipment panel.
 10. A spacecraft, comprising: a corestructure; an east-west equipment panel having an east end and a westend; an east radiator panel rotatably coupled to the east end of theequipment panel; a west radiator panel rotatably coupled to the west endof the equipment panel; a plurality of flexible heat pipes eachcomprising a first rigid tube thermally coupled to the east radiatorpanel, a second rigid tube coupled to the equipment panel, a third rigidtube thermally coupled to the west radiator panel, a first flexible tubesealingly coupled between the first and second rigid tubes; and a secondflexible tube sealingly coupled between the second and third rigidtubes; and one or more equipment modules thermally coupled to the secondrigid tube of at least one of the plurality of flexible heat pipes. 11.The spacecraft of claim 10, wherein: each of the plurality of flexibleheat pipes comprises a sealed first internal volume formed by therespective first, second, and third rigid tubes and the first and secondflexible tubes and a first heat transfer fluid disposed within the firstinternal volume; and the first and third rigid tubes of each of theplurality of flexible heat pipes are each capable of condensing thefirst heat transfer fluid from a vapor to a liquid by rejecting heat tothe respective east and west radiator panels.
 12. The spacecraft ofclaim 11, wherein the second rigid tube of each of the plurality offlexible heat pipes is capable of evaporating the first heat transferfluid from a liquid to a vapor by accepting heat from one or moreequipment modules thermally coupled to the second rigid tube.
 13. Thespacecraft of claim 11, wherein the first and third rigid tubes of eachof the plurality of flexible heat pipes are each capable of evaporatingthe first heat transfer fluid from a liquid to a vapor by accepting heatfrom the respective east and west radiator panels.
 14. The spacecraft ofclaim 10, further comprising a plurality of formed heat pipes eachcomprising a first portion thermally coupled to the second rigid tube ofa first flexible heat pipe, a second portion thermally coupled to thesecond rigid tube of a second flexible heat pipe and a third portionsealingly coupled between the first and second portions.
 15. Thespacecraft of claim 14, wherein each of the plurality of formed heatpipes are capable of transferring heat from the hotter of the first andsecond flexible heat pipes to the colder of the first and secondflexible heat pipes.
 16. The spacecraft of claim 14, wherein: each ofthe plurality of formed heat pipes further comprises a sealed secondinterior volume formed by the first, second, and third portions of therespective formed heat pipe and a second heat transfer fluid disposedwithin the second internal volume; each of the first and second portionsis capable of evaporating the heat transfer fluid from a liquid to avapor by accepting heat from the respective flexible heat pipe when therespective flexible heat pipe is the hotter of the first and secondflexible heat pipes; and each of the first and second portions iscapable of condensing the heat transfer fluid from a vapor to a liquidby rejecting heat to the respective flexible heat pipe when therespective flexible heat pipe is the colder of the first and secondflexible heat pipes.
 17. The spacecraft of claim 10, wherein at leastone of the east and west radiator panels is hingedly coupled to theequipment panel such that the at least one of the east and west radiatorpanels can be rotated to provide access to the one or more equipmentmodules.
 18. A method of controlling the temperature of an equipmentmodule on a spacecraft, the method comprising the step of: thermallycoupling the equipment module to a flexible heat pipe that comprises afirst rigid tube thermally coupled to an east radiator panel disposed onan external east surface of the spacecraft, a second rigid tubethermally coupled to a west radiator panel disposed on an external westsurface of the spacecraft, and a third rigid tube coupled to the firstand second rigid tubes by first and second flexible tubes, respectively,wherein the equipment module is thermally coupled to the third rigidtube.
 19. The method of claim 18, further comprising the steps of:moving one of the east and west radiator panels from a closed positionto an open position such that the respective one of the first and secondflexible tubes bends to maintain the integrity of the flexible heatpipe; attaching the equipment module to a equipment panel that iscoupled to the third rigid tube; and moving the one of the east and westradiator panels from the open position to the closed position.